Electrodes for the study of neurophysiological tissues have been disclosed. Gesteland et al. (Proceedings of the IRE (1959) 47:1856) provides a general review of electrodes and suggests the use of Ag-AgCl electrodes (pg. 1857). Electrodes have been used to study olfactory epithelia and the layer of mucus which overlays this tissue. These studies have provided records interpreted as receptor potentials in response to odorous stimulants. This measurement has been termed an "electro-olfactogram" (EOG).
Stimulation and recording of olfactory epithelia in many species have been disclosed. Ag-AgCl, agar-saline electrodes for olfactory measurement are disclosed in Ottoson, D., Acta Physiol. Scand. (1954) 32:384, in rabbits; Gesteland, R. C., et al., J. Physiol. (1965) 181:525, in frogs; Mackay-Sim, A., et al., J. Neurophysiol. (1982) 48:584, in salamanders; and, Thommesen, G., Acta Physiol. Scand. (1982) 115:47, in char.
General review of the measurement of electro-olfactograms (EOG) is provided by Takagi, S. F., in Olfaction and Taste, Pfaffmann, ed. (1969) 3:71; Ottoson, D., in Handbook of Sens. Physiol, (1974) 4:95; and, Gesteland, R. C., in Handbook of Sens. Physiol. (1974) 4:132.
Devices for the delivery of vapors, particularly to olfactory epithelia, have also been disclosed. These devices, which generally combine a constant air flow with the ability to introduce liquid odorous compounds in order to form a stimulatory vapor, have been termed "olfactometers" (Tucker, D. and T. Shibuya, Cold Spring Harbor Symp Quant. Biol. (1965) 30:207). Vigouroux, M., et al. (J. Neurosci. Methods (1988) 24:57) describe a wide concentration range olfactometer for delivery of short reproducible odor pulses.
Plattig, K. H. and G. Kobal (in Food Intake and Chem. Senses, Katsuki, Y., et al. eds. (1977) University Park Press, Baltimore pgs. 51-70) describe a device for olfactory stimulation and recording in humans. Since the delivery of stimulus is external to the nose the device is not precise with regard to the region or type of tissue stimulated.
An embodiment of the subject invention relates to the stimulation of a heretofore poorly understood neuroepithelial structure, commonly known as the vomeronasal organ ("VNO"; also known as "Jacobson's organ"). This organ is located bilaterally in the nostrils of most higher animals--from snakes to humans, and has been associated, inter alia, with pheromone reception in certain species (see generally Muller-Schwarze & Silverstein, Chemical Signals, Plenum Press, New York (1980)). The VNO is a small nasal organ with a central lumen and a pit opening to the nasal cavity. The VNO is a bilateral structure located supra palatial. The pit is approximately 1 to 1.5 mm in diameter and the lumen is approximately 1 to 1.5 cm deep. The lumen is lined with sensory neuroepithelia which constitute a distinct locus of olfactory receptors. The axons of the VNO neuroepithelia synapse with the auxiliary olfactory bulb and the amygdala, both in the brain, and from there, to the hypothalamus. Johnson, A. et al. (J. Otolaryngology (1985) 14:71-79) report evidence for the presence of the vomeronasal organ in most adult humans, but conclude that the organ is probably non-functional. Contravening results which suggest that the VNO is a functional chemosensory receptor are reported by Stensaas, L., et al. (submitted for publication).